Dimming (DALI, DSI ....)

Dimming means reducing the light output below the standard maximum level of the ballast or fitting. A dimming control system of some type is normally used to provide the necessary functionality. This may be a simple stand alone solution for a single circuits, or a zone of lighting. Or it may be a building wide switching and dimming lighting control system.

Not every lamp is dimmable, and it is important to establish first that the fittings to be dimmed are able to do so!

Intelligent Environments Ltd specialise in creating simple dimming systems. Whether you require assistance with DALI lighting control, with dimming DSI or analogue lighting or with dimming LEDs, speak to us about your options.

There are two types of signals that can control dimming operations, analogue and digital :

Analogue

An analogue signal can be received by a non-digital ballast or transformer for example, magnetic ballasts or low voltage electronic transformers. The dimming is achieved either by regulating the voltage (as with magnetic ballasts), or where dimming by electronic transformers by affecting either the trailing or leading edge of the current. Although many modern transformers dim by both trailing and leading edge methods, t is still important that compatibility is carefully checked.

It should be noted that although an analogue signal can be used with a rotary dimmer, this is not the case with a digital signal. If digital ballasts are used, they cannot be used with a manual rotary dimmer.

Digital

With digital the signal is received by electronic ballasts that commands the ballast to reduce the voltage supplied to the fitting.

Advantages include energy savings through reduced output, greater flexibility to respond to lighting requirements, and longer lamp life through the soft start for the lamp and the reduction of fluctuations in the voltage which cause flickering.

Further information on dimming protocols and products can be found below:

DALI

DALI stands for Digital Addressable Lighting Interface. The DALI protocol is managed under IEC standard 62386, recognised internationally as a global standard for professional digital lighting. The ‘open protocol’ means, in principle, a DALI lighting system can be composed of components from multiple manufacturers, all working from the same standard. As with all products however, individual DALI components can still vary considerably in quality and longevity according to supplier.

All you need to know about DALI

DALI stands for Digital Addressable Lighting Interface. The DALI protocol is managed under IEC standard 62386, recognised internationally as a global standard for professional digital lighting. The ‘open protocol’ means, in principle, a DALI lighting system can be composed of components from multiple manufacturers, all working from the same standard. As with all products however, individual DALI components can still vary considerably in quality and longevity according to supplier.

The DALI standard covers not just ballasts but control gear including LED drivers, switching devices, emergency inverters, colour controllers, and the control devices such as presence detectors, lux level sensors, switches, etc, as well as bus power supply requirements.

A DALI lighting control system where dimming and individual control can be provided, can be a source of significant energy savings. When dimmable drivers, presence detectors and lux level sensors are installed with appropriate parameters programmed, savings of up to 80% are achievable.

An additional advantage with DALI lighting controls is the ability to make changes via programming only, rather than the high costs involved in re-arranging or re-grouping lights in a fixed output system.

The two-way communication that can be provided with a DALI system allows for easier monitoring of energy consumption, and lamp condition, and can also provide automatic testing and reporting of emergency lighting.

The electrical manufacturers supplying DALI compliant products must be DALI members and their products must bear the DALI trademark. A list of members can be found at www.dali-ag.org

By using an interface between a DALI system, and another protocol, it is acceptable to connect multiple systems together. For example connecting a wireless system to DALI enables the luminaires to be wired, and therefore low-cost, but allows for the convenience of wireless in terms of sensors and switches. DALI interfaces well with a number of protocols including those commonly used in New Zealand such as C-Bus and KNX, and the CP Electronics range of standalone DALI lighting controls.

A DALI project may be as large as required, allowing thousands of devices to be connected to a single system. Or it could simply consist of a single luminaire with an on-board driver and sensor!

DSI

DSI (Digital Serial Interface) was a precursor to DALI. Developed by Tridonic in 1991 it was one of the first proprietary protocols to digitally control electrical ballasts.

Hard-wired groups of luminaires are given a DSI instruction to follow. Every ballast that is physically wired to a particular control group, will dim as that group. Individual DSI ballasts are not uniquely addressable as is the case with DALI.

All you need to know about DSI

DSI (Digital Serial Interface) was a precursor to DALI. Developed by Tridonic in 1991 it was one of the first proprietary protocols to digitally control electrical ballasts.

Hard-wired groups of luminaires are given a DSI instruction to follow. Every ballast that is physically wired to a particular control group, will dim as that group. Individual DSI ballasts are not uniquely addressable as is the case with DALI.

As DSI ballasts can set the light level to zero, many see this as meaning they can “switch the lights off”. This is not really correct as the lights are drawing standby current even when there is no light output as such.

DSI can be interfaced with a lighting control system such as C-Bus or KNX via a system gateway.

Although not as flexible as DALI in some situations it is considered an advantage that the ballast is not addressable, as when one fails, it can simply be replaced without further programming being required.

Large DSI installations however can require expensive and complex runs of multi-core cable.

0-10v (Analogue)

One of the earliest, and simplest ways of controlling lights, 0-10V or analogue is still widely used to control dimming functions for fluorescent ballasts and LED drivers for commercial and industrial lighting. The dimming range of the power supply or ballast is often limited. If light output can only be dimmed to 10% then a relay or switch must be provided to turn off all power to the system, and therefore turn the light completely off.

All you need to know about 0-10v (analogue)

One of the earliest, and simplest ways of controlling lights, 0-10V or analogue is still widely used to control dimming functions for fluorescent ballasts and LED drivers for commercial and industrial lighting. The dimming range of the power supply or ballast is often limited. If light output can only be dimmed to 10% then a relay or switch must be provided to turn off all power to the system, and therefore turn the light completely off.

For dimmable fluorescent lights the analogue system works at 1-10v, and is now often being superceded by DSI or DALI.

Analogue remains a popular system with some as it is easy to understand, install and to trouble shoot! Additionally its low current (typically 1mA) allows it to be run along relatively thin cables with little drop in voltage. It does require a wire per control channel however, plus a common return wire. A large and complex installation could therefore have hundreds of wires, requiring expensive multi-core cabling and abundant connectors. Interference from nearby AC power cables can also affect signals to the fitting, even to the extent of causing flickering.

It should be noted that although a 1-10v system is considered low voltage, it should still be treated with caution as a mains voltage to earth could still occur if there was a fault on the light fittings.

LEDs

The lower power, longer lifespan benefits offered by modern LED technology is resulting in huge migration from traditional incandescent and fluorescent lighting. Not just for general illumination, but in digital signage and for decorative lighting, taking advantage of the high level of versatility that LED based lighting can deliver.

All you need to know about dimming LEDs

The lower power, longer lifespan benefits offered by modern LED technology is resulting in huge migration from traditional incandescent and fluorescent lighting. Not just for general illumination, but in digital signage and for decorative lighting, taking advantage of the high level of versatility that LED based lighting can deliver. Read more . . .

With more and more LEDs being specified, it is crucial that the consultants responsible for creating the lighting system design are confident that the LEDs proposed in their design, can deal with the potentially harsh operational or environmental conditions that they may be exposed to.

Traditional ballasts tend to mask fluctuations in power with minor surges or spikes having little visible effect, although decreasing the life of the lamp. LED lighting however responds immediately to any slight change in power, and the result is visible as a higher pulse or flash of light.

The LED driver is therefore crucial to ensure fluctuations in power do not affect light output, or life of the LEDs. Commercial LED fittings are commonly being incorporated into DSI and DALI systems, or can be controlled by 0-10v analogue systems.

Suppliers/installers of lighting control systems such as ourselves, are the first to be blamed when lights appear to be ‘flickering’ when operating at a dimmed level. Unfortunately LED dimmer performance is almost totally determined by the driver capability and compatibility with the dimming system.

Our advice is to ALWAYS test to ensure compatibility before final decision is made on the choice of fittings. Intelligent Environments Ltd are always happy to test LED fittings/drivers for compatibility in our workshop, prior to sign off.

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